Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
  • H01H33/70—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid
  • H01H33/76—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid wherein arc-extinguishing gas is evolved from stationary parts; Selection of material therefor
  • H01H33/765—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid wherein arc-extinguishing gas is evolved from stationary parts; Selection of material therefor the gas-evolving material being incorporated in the contact material

Definitions

• the invention is based on a material with arc extinguishing properties according to the preamble of claim 1.
• a material with arc extinguishing properties according to the preamble of claim 1.
• Such a material is known from US Pat. No. 4,011,426.
• the known material is essentially characterized in that, in addition to arc-extinguishing components, it also has components which give it electrical conductivity. It is thereby achieved that the arc to be extinguished can burn directly between electrodes which are made of such material with arc-extinguishing properties or are equipped or coated with it.
• the excellent extinguishing effect of these materials is based on the fact that the arc is extinguished mainly by the processes taking place in the arc base points.
• Chemical compounds containing fluorine, etc. such as polytetrafluoroethylene can be produced; on the other hand, it should be electrically conductive, for which purpose it contains powder of silver or copper or nickel or iron or of their alloys, and should have as little erosion as possible (high resistance to arcing).
• the invention has for its object to improve a material of the type mentioned in such a way that the proportion of the electrically conductive metal can be reduced while maintaining sufficient electrical conductivity and the proportion of the components favoring the arc quenching can be increased.
• the saved electrically conductive metal can be replaced by an arc-quenching substance, which directly increases the arc-quenching effect and service life of an electrode made from the material according to the invention. It also has a favorable effect on the erosion and thus on the service life if one or more of the arc-extinguishing components of the material are coated with the electrically conductive metal, for example quartz sand, glass powder or calcium fluoride powder. Quartz sand or glass powder are examples of the inorganic constituents of the material melting higher than the electronegative gas-releasing substances; these do not release quenching gases under the influence of an arc, but they do limit the current in the arc and cool the arc. Other examples of such substances are silicon powder, aluminum oxide powder and dolomite powder.
• Plastics are primarily considered as binders for the materials according to the invention, especially curable one- and two-component resins (thermosets) such as epoxy resins, phenolic resins, urea resins, melamine resins and silicone resins.
• Resins as binders have the advantage that the materials according to the invention can be produced as spreadable, liquid to pasty preparations, which the user can further process as required, by producing arc-extinguishing moldings from these preparations by pouring and curing, or by spreading them on carriers (e.g. on metallic extinguishing plates in circuit breakers or fuses or on the housing walls of arcing chambers for Circuit breaker) manufactures components with an arc-extinguishing coating.
• carriers e.g. on metallic extinguishing plates in circuit breakers or fuses or on the housing walls of arcing chambers for Circuit breaker
• Thermoplastic materials are also suitable as binders insofar as they can absorb fillers.
• binders include polyamides, polypropylene, polyethylene terephthalate and polybutylene terephthalate. These binders have the advantage that they enable the rational production of arc-quenching moldings by injection molding.
• the aim should be to keep the content of the carbon-containing organic binders as low as possible in order to obtain as little carbon-rich decomposition products and soot as possible under the influence of an arc.
• those binders should be chosen that have a particularly high resistance to arcing.
• inorganic binders can also be used, e.g. Water glass (potassium silicate and / or sodium silicate) or low melting enamel.
• the material according to claim 5 differs from the material according to claim 1 in that its electrical conductivity is also anisotropic due to the anisotropic distribution of the metallic components.
• Anisotropic distribution of the electrically conductive metal makes it possible to guide the current paths in a shaped part (electrode) made of the material in such a way that the current paths from a current connection point of the shaped part preferably lead to that surface area of the shaped part - and there preferably perpendicular to the surface of the molded part are oriented - on which the arc base points lie or - better said - should migrate.
• Another possibility of saving on electrically conductive metal due to its anisotropic distribution is to provide the electrically conductive metal in the form of a predominantly flaky powder (claim 7). This possibility is particularly important if a hardenable synthetic resin is used as the binder. If the not yet hardened, still liquid or pasty material is applied as a coating to a support or if it is filled into a mold to form shaped bodies, then a preferred orientation of the flaky metal powder particles is formed such that the scales are preferably parallel to one another . This favors the overlap of neighboring scales and with it the formation of current paths in this preferred direction.
• Another possibility of achieving anisotropy in the distribution of the electrically conductive metal is to embed it in the form of a fabric in the material, which allows the arc-quenching gases to pass through and increases the mechanical strength of the material (claim 8).
• the material with arc extinguishing properties contains 30% by weight of finely ground quartz sand, 20% by weight of silver, 25% by weight of polytetrafluoroethylene powder, 5% by weight of sulfur powder and 20% by weight of a two-component epoxy resin.
• the quartz sand is coated with the silver using a chemical coating process (i.e. without electricity).
• the coated silica sand, the PTFE - powder and the sulfur powder are stirred into the still liquid epoxy resin formulation, the mixture is poured into molds and cured at elevated temperature.
• the shaped bodies thus produced are suitable as arc-quenching electrodes in switching devices and fuses.
• the material with the composition mentioned in Example 1 is produced by stirring the fillers into an epoxy resin base which does not yet contain any curing component.
• the spreadable paste and hardener are filled separately and delivered to the user and only mixed by the user before use.
• the material is suitable for coating quenching chamber components and arcing horns in overvoltage protection devices, lightning protection devices or in traction current phase isolators, which are used to extinguish arcs between adjacent contact wire ends for electric rail vehicles.
• the material consists of 25% by weight of nickel fibers with a diameter of approx. 10 ⁇ m, 20% by weight of calcium fluoride powder, 20% by weight of barium sulfate powder, 10% by weight of dolomite powder and 10% by weight of finely ground quartz sand and 15% by weight. -% of a curable melamine resin.
• the powdery fillers are stirred into the still liquid resin base and then the bundled nickel fibers are placed in an elongated form and poured with the resin mixture containing the powdery fillers. After the resin has hardened, the moldings are trimmed. They are suitable as arc extinguishing electrodes in switching devices.
• Examples 1 and 2 are modified in such a way that the silver is not coated on the quartz sand, but instead the quartz sand and the silver are introduced separately into the material, namely the silver as a powder of predominantly platelet-shaped structure, which is obtained from dendritic silver powder by grinding was obtained in a ball mill.
• the material contains 30% by weight of polytetrafluoroethylene powder, 20% by weight of finely ground quartz sand, 20% by weight of copper, 5% by weight of sulfur powder and 25% by weight of polyethylene terephthalate as a binder.
• the quartz sand is electrolessly coated with the copper and then dry together with the PTFE powder and the sulfur powder mixed with a fine-grained polyethylene terephthalate granulate and processed to shaped bodies on an injection molding machine.
• the moldings are suitable as arc-quenching components, in particular electrodes and quenching plates or quenching rings in switching devices and fuses.

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Citations (5)

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• 1983
  • 1983-04-09 DE DE19833312852 patent/DE3312852C2/de not_active Expired
• 1984
  • 1984-03-01 EP EP84102176A patent/EP0123823A1/fr not_active Withdrawn
  • 1984-04-09 JP JP7072184A patent/JPS59196527A/ja active Pending

Patent Citations (5)

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